This invention relates to a manually operated, power assisted vehicle such as a wheelchair and more particularly to an improved control arrangement therefor.
A wide variety of types of vehicles have been proposed that are designed to be operated primarily by manual power. Although these vehicles are primarily land vehicles, the same concept can be applied to vehicles traveling over other types of terrain, for example, water.
For a variety of reasons, it has also been proposed to provide a prime mover assist for these vehicles. One very popular and successful type of vehicle of this nature employs an arrangement wherein the amount of power assists supplied is dependent upon the degree or presence of manual power asserted by the vehicle occupant. There are a number of advantages of this type of vehicle.
First, by ensuring that the power assist is provided only in response to a manual power input force, a certain degree of safety is assured. Furthermore, this type of vehicle permits the rider to obtain physical exercise at the same time he is traveling. Finally, this type of system has an advantage for disabled or physically challenged persons because they will still have the psychological assurance that they are able to travel by themselves.
In order to obtain this type of control, some sensor must be employed in the vehicle that senses the actual force applied by the rider or occupant. Frequently, potentiometers are utilized as the sensors although other types of sensors may be employed. Potentiometers are frequently used where the prime mover is an electric motor, although the application is not so limited.
As with all control systems, the sensor has a null or dead band area wherein some degree of movement is provided without the resulting output of a signal. This means that the sensor must be relatively accurate. This also means that the sensor must be relatively accurately positioned with respect to the component with which it cooperates so that this dead band does not cause improper functioning of the total control system.
Although these types of adjustments can be easily made at the factory where the component is manufactured, difficulties arise in connection with either the servicing or the periodic adjustment of the system when it is in use by the owner. The necessity for facilitating and simplifying the adjustment is particularly important when the user is a disadvantaged or physically challenged person.
It is, therefore, a principle object of this invention to provide an improved manually operated, power assisted vehicle.
It is a further object of this invention to provide an improved force sensor and mounting and adjustment mechanism for such a type of vehicle.
It is a still further object of this invention to provide an improved adjusting mechanism for the force sensor of such a vehicle wherein the number of tools and instruments required to make adjustment are minimized.
It is a yet further object of this invention to provide an improved sensor and adjustment mechanism that can be easily adjusted by the user even while in the vehicle.
Because of its excellent applicability to utilization by disabled persons, the type of power assisted, manually operated system described is frequently employed in conjunction with wheelchairs.
To apply this system to a wheelchair, it is desirable to associate the force sensor with the hand rim that the occupant of the wheelchair normally uses for manual propulsion. In other words, the hand rim is mounted for limited relative rotation relative to the associated wheel. This degree of relative rotation is utilized in conjunction with a spring and sensor so as to provide a way of sensing of the manual input force.
It is, therefore, a still further object of this invention to provide an improved force sensor and adjustment mechanism therefor that can be utilized with the hand rim of a power assisted wheelchair.
The wheelchair presents certain particular problems in connection with the coupling of the hand rim to the wheel and particularly where the hand rim is rotatable to a limited extent relative to the wheel. Obviously, the hand rim and wheel have fairly large diameters. The operator, by the very nature of the mechanism, applies not only a circumferential force to the hand rim but also a force that acts normally to the axis of rotation. This force acts through a fairly large moment arm and thus can put bending forces on the hand rim. These can cause difficulties to occur in the transmission of the forces to the sensor and can also cause binding when the system is being operated.
It is, therefore, a still further object of this invention to provide an improved connection and bearing arrangement for the hand rim of a wheelchair utilizing a power assist mechanism and associated sensor.